Author: asomers
Date: Wed Sep 11 18:54:45 2019
New Revision: 352229
URL: https://svnweb.freebsd.org/changeset/base/352229

Log:
  ping: Verify whether a datagram timestamp was actually received.
  
  ping(8) uses SO_TIMESTAMP, which attaches a timestamp to each IP datagram at
  the time it's received by the kernel.  Except that occasionally it doesn't.
  Add a check to see whether such a timestamp was actually set before trying
  to read it.  This fixes segfaults that can happen when the kernel doesn't
  attach a timestamp.
  
  The bug has always existed, but prior to r351461 it manifested as an
  implausible round-trip-time, not a segfault.
  
  Reported by:  pho
  MFC after:    3 days
  MFC-With:     351461

Modified:
  head/sbin/ping/ping.c

Modified: head/sbin/ping/ping.c
==============================================================================
--- head/sbin/ping/ping.c       Wed Sep 11 18:48:26 2019        (r352228)
+++ head/sbin/ping/ping.c       Wed Sep 11 18:54:45 2019        (r352229)
@@ -931,7 +931,8 @@ main(int argc, char *const *argv)
                                continue;
                        }
 #ifdef SO_TIMESTAMP
-                       if (cmsg->cmsg_level == SOL_SOCKET &&
+                       if (cmsg != NULL &&
+                           cmsg->cmsg_level == SOL_SOCKET &&
                            cmsg->cmsg_type == SCM_TIMESTAMP &&
                            cmsg->cmsg_len == CMSG_LEN(sizeof *tv)) {
                                /* Copy to avoid alignment problems: */
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